Press machine and pressing method

ABSTRACT

A press machine includes a lower die having a step portion for forming a bent portion on a side surface, a pad portion supported by a spring and disposed adjacent to the lower die in the horizontal direction, being movable upward and downward, an upper die disposed opposing the pad portion in the vertical direction, and a regulation portion. When the upper die moves downward and presses a steel plate between the upper die and the pad portion to form a bent portion in an edge portion of the steel plate, the regulation portion moves together with the upper die and regulates the motion of the edge portion of the steel plate protruding from the lower die in the horizontal direction, thereby preventing a wrinkle from forming in the edge portion of the steel plate.

CROSS-REFERENCE OF THE INVENTION

This application claims priority from Japanese Patent Application No. 2014-016719, filed on Jan. 31, 2014, the content of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a press machine and a pressing method for forming a bent portion in an edge portion of a steel plate.

2. Description of the Related Art

For vehicle components, a thinned and high-strength member is used so as to enhance both the safety and economy. For this purpose, so-called hot press is known in which a steel plate heated to high temperature is quenched by cooling the plate with low-temperature press dies. In this method, a steel plate is heated to an austenitizing temperature or higher, and the steel plate is formed and rapidly cooled with a press machine simultaneously, completing quenching.

A certain kind of vehicle component has a bent portion (step portion) with an L-shaped cross-section in the edge portion of the steel plate. A press machine is used when such a bent portion is formed by the hot press, which has a lower die having a step portion for forming a bent portion on a side surface, a pad portion disposed adjacent to the lower die in the horizontal direction, and an upper die disposed opposing the pad portion in the vertical direction.

In this press machine, when the upper die is moved downward, a steel plate as a member to be pressed is pressed between the upper die and the pad portion to form a bent portion in the edge portion of the steel plate by utilizing the step portion of the lower die for forming a bent portion. A relevant technique is disclosed in Japanese Patent Application Publication No. 2011-152547.

However, when the upper die is moved downward to draw the steel plate toward the step portion of the lower die, a wrinkle occurs in the end portion of the steel plate. As the wrinkle is larger, the steel plate is more likely to be folded partially in the wrinkle portion. Although the wrinkle may be smoothed by being pressed at the end, there is a problem of decreasing the strength in the portion.

SUMMARY OF THE INVENTION

According to the examination by the inventor, as shown in FIG. 6, it was found that when a step height 101 of a bent portion of a steel plate 100 is large and the edge portion of the steel plate 100 is curved, a wrinkle 103 occurs in the curved portion 102 and the steel plate 100 is significantly folded, and these problems significantly occur by the hot press of pressing the heated and soften steel plate 100 although it may also occur by the cold press. This invention is directed to this problem.

A press machine includes a lower die having a step portion on its side surface, a pad portion supported by a spring and disposed adjacent to the lower die in a horizontal direction, an upper die disposed opposing the pad portion in the vertical direction, and a regulation portion movable together with the upper die upward and downward in the vertical direction. The pad portion is movable upward and downward in the vertical direction. The upper die and the pad portion are configured to hold a steel plate between them, the lower die is configured to form a bent portion at an edge portion of the steel plate held between the upper die and the pad portion, when the upper die and the regulation portion move downward, and the regulation portion is configured to regulate a movement of the edge portion of the steel plate protruding from the lower die in the horizontal direction, when the bent portion is formed.

Furthermore, a pressing method includes providing a press machine including a lower die having a step portion on its side surface, a pad portion supported by a spring and disposed adjacent to the lower die in the horizontal direction, an upper die disposed opposing the pad portion in the vertical direction, and a regulation portion movable together with the upper die upward and downward in the vertical direction. The pad portion is movable upward and downward in the vertical direction. The method also includes heating a steel plate to an austenitizing temperature or higher, mounting the heated steel plate on the lower die and the pad portion, moving the upper die and the regulation portion downward so as to hold the steel plate between the upper die and the pad portion, moving the upper die and the regulation portion further downward so as to form a bent portion at an edge portion of the steel plate between the lower die and the upper die that is moved further downward, and regulating a movement of the edge portion of the steel plate protruding from the lower die in the horizontal direction so as to prevent a wrinkle from forming in the edge portion of the steel plate, when the bent portion is formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a press machine of an embodiment of the invention.

FIG. 2 is a cross-sectional view of the press machine of the embodiment of the invention.

FIG. 3 is a cross-sectional view of the press machine of the embodiment of the invention.

FIG. 4 is a cross-sectional view of the press machine of the embodiment of the invention.

FIG. 5 is a partial plan view of the press machine of the embodiment of the invention.

FIG. 6 is a perspective view of a pressed steel plate.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the invention will be described referring to the figures. FIG. 5 is a partial plan view of a press machine 10, and FIGS. 1 to 4 are cross-sectional views of FIG. 5 along line X-X.

As shown in the figures, a lower die 1 is fixed on a base 2 and has a step portion 3 for forming a bent portion on a side surface. A pad portion 4 is disposed adjacent to the lower die 1 on the step portion 3 side in the horizontal direction. A portion of one side surface of the pad portion 4 is in contact with the lower side surface of the lower die 1 below the step portion 3.

The pad portion 4 is supported by a spring 5 (e.g. a gas spring) disposed on the base 2, being movable upward and downward.

An upper die 6 is disposed opposing the pad portion 4 in the vertical direction. A regulation portion 7 is disposed adjacent to the upper die 6 in the horizontal direction on the outside of the end of the lower die 1 in the horizontal direction. As shown in the cross-sectional view of FIG. 1, the regulation portion 7 has a flat lower end surface in the similar manner to the upper die 6, and has a shape protruding downward as a whole. The upper die 6 and the regulation portion 7 are configured so as to be driven upward and downward by a drive device (not shown) in order to press a steel plate 100 as a member to be pressed. As shown in a partial plan view of FIG. 5, the lower die 1 and the regulation portion 7 are curved as a whole along the edge portion of the steel plate 100, the edges of the pad portion 4 and the upper die 6 are curved along the inner side of the curved portion of the lower die 1, and the step portion 3 of the lower die 1 is disposed between the lower die 1 and the pad portion 4. The upper die 6 and the regulation portion 7 may be formed integrally as an upper die.

When the upper die 6 is moved downward to press the steel plate 100 between the upper die 6 and the pad portion 4 and form a bent portion in the edge portion of the steel plate 100, the regulation portion 7 moves downward together with the upper die 6 and regulates the motion of the edge portion of the steel plate 100 protruding from the lower die 1 in the horizontal direction so as to prevent a wrinkle from forming in the edge portion of the steel plate 100. In particular, as shown in FIG. 6, when the step height 101 of the bent portion of the steel plate 100 is large such as 120 to 150 mm and the edge portion of the steel plate 100 is curved, the effect of preventing a wrinkle is high.

Hereafter, a hot press method by the press machine 10 will be described.

First, the steel plate 100 is heated to an austenitizing temperature or higher by a furnace (not shown). Next, as shown in FIG. 1, while the upper die 6 and the regulation portion 7 are kept above at the top dead center, the heated steel plate 100 is carried from the furnace and mounted on the lower die 1 and the pad portion 4. In this case, the steel plate 100 extends from on the pad portion 4 through above the step portion 3 of the lower die 1 to protrude from the upper end surface of the lower die 1 in the horizontal direction.

Then, as shown in FIG. 2, the upper die 6 and the regulation portion 7 are moved downward. In the state shown in FIG. 2, while the steel plate 100 is held between the upper die 6 and the pad portion 4 and the lower end surface of the upper die 6 is in contact with the upper surface of the steel plate 100 mounted on the pad portion 4, it is preferable that the lower end surface of the regulation portion 7 is not in contact with the upper surface of the steel plate 100 yet.

In detail, in the state shown in FIG. 1, the height from the upper surface of the steel plate 100 to the lower end surface of the upper die 6 in the vertical direction is hl, and the height from the upper surface of the steel plate 100 to the lower end surface of the regulation portion 7 in the vertical direction is h2 which is larger than h1 (h2>h1). In the state of FIG. 2, the height from the upper surface of the steel plate 100 to the lower end surface of the regulation portion 7 in the vertical direction is h=h2−h1.

Then, as shown in FIG. 3, the upper die 6 and the regulation portion 7 are further moved downward. Then, the upper die 6 presses down the pad portion 4 on which the steel plate 100 is mounted against the repulsive force of the spring 5. The steel plate 100 is held by the pressure of the upper die 6 and the repulsive force of the spring 5. By this, the steel plate 100 is drawn toward the step portion 3 of the lower die 1, sliding along the upper surface of the lower die 1, to form a bent portion as well as be quenched.

On the way to forming the bent portion, the regulation portion 7 comes into contact with the upper surface of the steel plate 100, and regulates the motion of the edge portion of the steel plate 100, thereby preventing a wrinkle from forming in the edge portion of the steel plate 100 and preventing the steel plate 100 from folding. If the regulation portion 7 is not provided, the edge portion of the steel plate 100 is lifted up, resulting in a wrinkle in the edge portion of the steel plate 100.

In this case, by delaying the contact of the regulation portion 7 with the steel plate 100, the edge portion of the steel plate 100 is prevented from being rapidly cooled locally and the steel plate 100 is prevented from being broken by stress by being drawn.

Next, as shown in FIG. 4, the upper die 6 and the regulation portion 7 are further moved downward. Then the steel plate 100 is drawn toward the step portion 3 of the lower die 1 more deeply to make the bent portion larger, and the regulation portion 7 presses down the edge portion of the steel plate 100. In this case, in order to move the regulation portion 7 downward without contacting the lower die 1, the regulation portion 7 is disposed away from the lower die 1 in the horizontal direction. It is preferable that the distance d between the regulation portion 7 and the lower die 1 in the horizontal direction is larger than the thickness t of the steel plate 100 (d>t).

The press machine 10 of the embodiment has a high effect in preventing the wrinkle formation when it is applied to the hot press which tends to form a wrinkle, but it may also be applied to the cold press which does not heat the steel plate 100.

When a bent portion is formed in an edge portion of a steel plate by pressing, the invention prevents a wrinkle from forming in the edge portion and enhances the strength of the press member.

The effect is high particularly when the step height of the bent portion of the steel plate is large and the edge portion of the steel plate is curved. Furthermore, the invention has a high effect when it is applied to the hot press although it may also be applied to the cold press. 

What is claimed is:
 1. A press machine comprising: a lower die having a step portion on a side surface thereof; a pad portion supported by a spring and disposed adjacent to the lower die in a horizontal direction, the pad portion being movable upward and downward in a vertical direction; an upper die disposed opposing the pad portion in the vertical direction; and a regulation portion movable together with the upper die upward and downward in the vertical direction, wherein the upper die and the pad portion are configured to hold a steel plate therebetween, the lower die is configured to form a bent portion at an edge portion of the steel plate held between the upper die and the pad portion, when the upper die and the regulation portion move downward, and the regulation portion is configured to regulate a movement of the edge portion of the steel plate protruding from the lower die in the horizontal direction, when the bent portion is formed.
 2. The press machine of claim 1, wherein the regulation portion is disposed away from the lower die in the horizontal direction so as not to contact the lower die when the regulation portion moves downward, and a lower end surface of the regulation portion lies higher than a lower end surface of the upper die in the vertical direction.
 3. The press machine of claim 1, wherein the regulation portion is disposed away from an end of the upper die in the horizontal direction.
 4. The press machine of claim 3, wherein a distance between the regulation portion and the lower die in the horizontal direction is larger than a thickness of the steel plate.
 5. The press machine of claim 1, wherein the lower die and the regulation portion are curved as a whole along the edge portion of the steel plate.
 6. A pressing method comprising: providing a press machine comprising a lower die having a step portion on a side surface thereof, a pad portion supported by a spring and disposed adjacent to the lower die in a horizontal direction, an upper die disposed opposing the pad portion in a vertical direction, and a regulation portion movable together with the upper die upward and downward in the vertical direction, the pad portion being movable upward and downward in the vertical direction; heating a steel plate to an austenitizing temperature or higher; mounting the heated steel plate on the lower die and the pad portion; moving the upper die and the regulation portion downward so as to hold the steel plate between the upper die and the pad portion; moving the upper die and the regulation portion further downward so as to form a bent portion at an edge portion of the steel plate between the lower die and the upper die that is moved further downward; and regulating a movement of the edge portion of the steel plate protruding from the lower die in the horizontal direction so as to prevent a wrinkle from forming in the edge portion of the steel plate, when the bent portion is formed.
 7. The pressing method of claim 6, wherein the regulation portion is disposed away from the lower die in the horizontal direction so as not to contact the lower die when the regulation portion moves downward, and a lower end surface of the regulation portion lies higher than a lower end surface of the upper die in the vertical direction.
 8. The pressing method of claim 6, wherein the regulation portion is disposed away from an end of the upper die in the horizontal direction.
 9. The pressing method of claim 8, wherein a distance between the regulation portion and the lower die in the horizontal direction is larger than a thickness of the steel plate.
 10. The pressing method of claim 6, wherein the lower die and the regulation portion are curved as a whole along the edge portion of the steel plate. 